Generally, an apparatus for transceiving a video signal denotes a data transmission system in an asymmetric point-to-point application. The data transmission system may include a video signal transmission apparatus that can transmit video and auxiliary data and a video signal display apparatus that can receive the video and auxiliary data to display the same on a screen. The video signal transmission apparatus is generally referred to as a source such as a digital video disk (DVD) player, a set-top box, and the like. The video signal display apparatus is referred to as a sink such as a liquid crystal display (LCD) television (TV), a projector, and the like. The video signal display apparatus generally receives the video only to display a video signal on the screen. Therefore, there is no need to transmit control or data to the video signal transmission apparatus to thereby control or manage an operation of the video signal transmission apparatus. However, as can be shown in a High Definition Multimedia Interface (HDMI) that is generally used for a wired system and is a representative example of a video signal transceiving system, there is a need to transmit control or data to a video signal transmission apparatus even in the video signal display apparatus. In particular, in the case of an HD video, devices transmitting and receiving the HD video may need to frequently exchange data with each other for authentication in order to protect copyrights.
For this, the video signal transmission apparatus may need to acquire a downlink channel for transmitting video and auxiliary data. Also, the video signal display apparatus may need to acquire an uplink channel for transmitting control or user data. In this instance, various types of schemes may be adopted. For example, when frequency resources are sufficient, there is a scheme that can allocate another channel with a different frequency as an uplink channel to transmit control or user data via the allocated channel using a frequency division duplex (FDD) scheme. However, in this case, there is a need for a separate modulation/demodulation apparatus. Also, the frequency resources may be unnecessarily used. Therefore, a time division duplex (TDD) scheme is currently used. The TDD scheme can perform time division duplex for the same frequency to thereby more effectively use frequency resources and also can transmit data to a single modulation/demodulation apparatus to thereby solve the above problems in an inexpensive manner. The TDD scheme can transmit data in one time and receive data in another time using a single modulation/demodulation apparatus. Therefore, the TDD scheme may need to switch a mode of a radio frequency (RF) switch to a transmission mode or a reception mode. Generally, about 2 us may be required to switch the mode of the RF switch in a wireless transmission system. In order to receive data in a horizontal blanking interval (HBI) and to transmit data in an active line (AL), the video signal transmission apparatus may need to perform two switching procedures, for example, from a transmission mode to a reception mode and then from the reception mode to the transmission mode. Therefore, at least about 4 us may need to be acquired. The following Table 1 shows a screen resolution, a number of frames, and an occupancy time of an HBI according to a color depth. As shown in Table 1, when the screen resolution is 1080 p 60 f, the occupancy time of the HBI is only about 1.8 us. Therefore, the video signal display apparatus cannot transmit control or user data in this interval. Also, when considering the current tendency that the HD of the video signal transceiving apparatus is becoming more favored, it may be more difficult to transmit control or user data from the video signal display apparatus to the video signal transmission apparatus. For example, when transmitting a 60-frame video or 120-frame video, the occupancy time of the HBI is only about 0.9 us.
In comparison to using an occupancy time of an HBI that is not long enough to change the mode of the RF switch, the video signal display apparatus may transmit control or user data to the video signal transmission apparatus using a vertical blanking interval (VBI). For example, when the screen resolution is 1080 p 60 f, the occupancy time of the VBI is about 667 us and thus there may be no problem to allocate an uplink channel in this interval. However, since the VBI appears only 60 times per second for 1080 p 60 f, control or user data may not be immediately transmitted as required and may need to wait until the VBI appears.
TABLE 1RateRateHBIVBIFormatV FreqHRESVRESDE_CNTDE_LIN24 bit20 bit(sec)(sec) 640 × 48060800525640480192016006.34921E−060.001429 640 × 48072832520640480192016006.16371E−060.001068 640 × 48075840500640480192016006.34921E−060.000533 800 × 600601056628800600240020006.43376E−060.000743 800 × 60072104066680060024002000 4.8125E−060.001376 800 × 600751056625800600240020005.17172E−060.0005331024 × 7686013448061024768307225604.92339E−060.0007861024 × 7687013288061024768307225604.05735E−060.0006741024 × 7687513128001024768307225603.65854E−060.0005331024 × 7688513768081024768307225603.72472E−060.0005821280 × 1024601708106612801024384032003.91785E−060.0006571280 × 1024751708106612801024384032003.13428E−060.0005251280 × 1024851728107212801024384032002.84525E−060.000527 480i59.941716262/72048021601800 3.6852E−050.002802/2630.002918 480p60858525720480216018005.10601E−060.001429 720p6016507501280720384032004.98316E−060.0006671080i302200562/19201080576048003.77104E−060.000652/5630.0006811080p302200112519201080576048003.77104E−060.0013331080p602200112519201080576048001.88552E−060.000667
In the above Table 1, Format denotes a configuration of the screen resolution, V Freq denotes a vertical frequency, HRES denotes a horizontal resolution, VRES denotes a vertical resolution, DE_CNT denotes a data enable count, Rate 24 bit denotes a data amount of a single horizontal line (604×24/8=1920 bytes) when a color depth is 24 bits, Rate 20 bit denotes a data amount of a single horizontal line (640×20/8=1600 bytes) when the color depth is 20 bits, HBI denotes a horizontal blanking interval, and VBI denotes a vertical blanking interval.